DIN 53380-3-1998 Testing of plastics - Determination of gas transmission rate - Part 3 Oxygen-specific carrier gas method for testing of plastic films and plastics mouldings《测定塑料的气.pdf

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1、DEUTSCHE NORM Julv 19: Determining the gas transmission rate of plastic film, sheeting and mouldings by the carrier gas method DIN - 53380- ICs 83.1 40.1 O; 83.1 40.99 Descriptors: Plastics, film, sheeting, plastic mouldings, testing, gas transmission rate. Prfung von Kunststoffen - Bestimmung der G

2、asdurchlssigkeit - Teil 3: Sauerstoffspezifisches Trgergas- Verfahren zur Messung an Kunststoff-Folien und Kunststoff-Formteilen In keeping with current practice in standards published by the International Organization for Standardiza- tion (ISO), a comma has been used throughout as the decimal mark

3、er. Contents Page Foreword . 2 1 Scope . 2 2 Normative references . 2 3 Concepts 2 3.1 Area-related oxygen transmission rate . . 2 3.2 Volume-related oxygen transmission rate 2 3.3 Length-related oxygen transmission rate 2 Page 8.7 Load resistor 6 8.8 Voltage recorder . 6 9 Checking the sensor 6 10

4、Calibration constant . 6 11 Specimen preparation . 7 11.2 Hollow bodies 7 11.3 Number of specimens . 7 11.1 Film and sheeting . 7 12 Testing of film and sheeting 7 12.1 Diffusion cell . 4 Designation . 2 5 Principle 12.2 Procedure 5.1 Film or sheeting 12.3 Determining the zero le 6 Reagents 6.1 Carr

5、ier gas 6.2 Oxygen and ox 6.3 Vacuum grease . 3 13 Testing hollow bodies . . . 5.2 Hollow-bodies 3 12.4 Determining the oxyge rate transmission rate 8 12.5 Film or sheeting havin . . 6.4 Adhesives . 3 13.1 Closed bodies . 8 13.2 Open bodies . 10 13.3 Testing of tubes 7 Apparatus . 8 Components of di

6、ffusion cells . 8.1 Joints . 8.2 Humidification components 8.3 Components for removal of oxygen from carrier gas . 8.4 Flowmeter . 8.5 Valves .5 .5 .5 1 1 1 5 5 51 4 Evaluation 4.1 Area-related oxygen transmission rate 4.2 Volume-related oxygen transmission rate . 4.3 Length-related oxygen transmiss

7、ion rate . 11 11 8.6 Sensor . 5 15 Test report . 11 Continued on pages 2 to 11. Translation by DIN-Sprachendienst. In case of doubt, the German-language original should be consulted as the authoritative text. Q No pari of this translation may be reproduced without the prior permission of Beuth Verla

8、g GmbH, D-10772 Berlin, hac the exclusive right of sale for German Standards (DIN-Normen). Ref. No. DIN 53380-3 : 1998-07 DIN Deutsches Institut fr Normung e. V., Berlin. English price group 08 Sales No. 0108 11.99 Page 2 DIN 53380-3 : 1998-07 Foreword This standard has been prepared by Technical Co

9、mmittee Kunststoff-Folien und kunststoffbeschichtete Flachen- gebilde (Kunstleder); allgemeine Eigenschaften of the Normenausschu Kunststoffe (Plastics Standards Com- mittee). It is based on ASTM D 3985-95, but, unlike the ASTM Standard, its application is not limited to film and sheeting, and it al

10、so covers plastic hollow bodies (such as packing containers and tubes). Details of humidifying the carrier gas have also been included. 1 Scope The method specified in this standard serves to determine the oxygen transmission rate (permeability to pure oxygen or oxygen gas mixtures, e.g. air) of pla

11、stic film and sheeting as defined in DIN 16922 and plastic hollow bodies (e.g. packaging containers, plastic tubes), thereby enabling their suitability for packaging and engineer- ing applications to be assessed. The method can be used to determine transmission rates ranging from about 0,05 cm3/(m2

12、. d . bar) to 1 O00 cm3/(m2 . d . bar) for film and sheeting and from about 0,0005 cmV(d . bar) to 1 O cmV(d . bar) for hollow bodies, where d denotes a day as a unit of 24 hours. 2 Normative references This standard incorporates, by dated or undated reference, provisions from other publications. Th

13、ese norma- tive references are cited at the appropriate places in the text, and the titles of the publications are listed below. For dated references, subsequent amendments to or revisions of any of these publications apply to this standard only when incorporated in it by amendment or revision. For

14、undated references, the latest edition of the publication referred to applies. DIN 1343 Reference conditions, standard conditions and standard volume - Concepts and values DIN 16922 Classification of flexible sheeting produced using plastics DIN 50008-1 Artificial climates in technical applications

15、- Controlled atmosphere over saturated salt solutions and glycerol solutions DIN 53370 Determination of plastic film and sheeting thickness by mechanical scanning ASTM D 3985-95 Standard test method for oxygen gas transmission rate through plastic film and sheeting using a coulometric sensor 3 Conce

16、pts 3.1 Area-related oxygen transmission rate For flat specimens of a constant thickness (such as film or sheeting), the area-related oxygen transmission rate is the volume of oxygen at standard temperature and pressure) which passes through the specimen per unit area, time and oxygen partial pressu

17、re. 3.2 Volume-related oxygen transmission rate For hollow bodies with an unknown surface area or a varying wall thickness, the volume-related oxygen transmission rate is the volume of oxygen at standard temperature and pressure) which passes through the specimen per unit time and oxygen partial pre

18、ssure. 3.3 Length-related oxygen transmission rate For tubes, the length-related oxygen transmission rate is the volume of oxygen at standard temperature and pressure) which, for given cross-sectional dimensions of the tube, passes through the specimen per unit length of tube, time and oxygen partia

19、l pressure. 4 Designation Designation of the method of determining the gas transmission rate by the carrier gas method (S): Test DIN 53380 - S I) See DIN 1343 for definition. Page 3 DIN 53380-3 : 1998-07 5 Principle The oxygen transmission rate is determined under the conditions given below by measu

20、ring the quantity of oxygen which passes through the specimen. 5.1 Film or sheeting A specimen is mounted as a sealed barrier between the two chambers of a cell. One chamber is purged with a stream of nitrogen, the other chamber contains oxygen. As oxygen passes through the specimen, it is transport

21、ed to a coulometric sensor where it produces an electrical current, the magnitude of which is propor- tional to its concentration in the gas flow (cf. clause 1 O). 5.2 Hollow bodies Nitrogen is passed directly through a hollow body whose exterior is exposed to oxygen. 6 Reagents 6.1 Carrier gas The

22、carrier gas shall be dry nitrogen containing 0,5 YO to 3 YO (V/V) hydrogen and not more than 0,Ol YO (V/V) oxygen. High-purity (99,9990) nitrogen may be used as the carrier gas in equipment as described in sub- clause 8.3. 6.2 Oxygen and oxygen-gas mixture The oxygen gas used shall be dry and shall

23、contain not less than 99,5 YO (V/V) of oxygen or oxygen-gas mixtures (preferably, oxygen containing nitrogen) free of carbon dioxide (cf. subclause 8.6) and having an oxygen content known to within 0.5 YO. 6.3 Vacuum grease Vacuum grease shall be used to seal the diffusion cell. 6.4 Adhesives A gas-

24、impermeable, pore-free, two-part adhesive shall be used when testing hollow bodies; fast-curing adhe- sives based on methyl methacrylate or adhesives based on epoxy resin are recommended. Page 4 DIN 53380-3 : 1998-07 Testing of film sheeting (as in clause 12) Testing of hollow bodies (as in clause 1

25、3) 7 Testing of tubes (as in subclause 13.3) AH v1 v2 K B G S D L T O L =.el D T w AH It Connection to diffusion cell Valve Valve Metal tube, filled with platinum catalyst or oxygen absorbent Gas washing bottle, for humidifying the carrier gas where a low relative humidity of carrier gas is required

26、 Gas washing bottle, for establishing specific humidities in the test gas Coulometric sensor Flowmeter and valve, for setting carrier gas flow Load resistor Compressed gas steel cylinder containing carrier gas (with pressure reducing valve and pressure gauge) Compressed gas steel cylinder containing

27、 oxygen (with pressure reducing valve and pressure gauge) Figure 1 : Test apparatus (schematic) 2, Information on sources of supply is available from Normenausschu Kunststoffe, Burggrafenstrae 6, D-10787 Berlin. Page 5 DIN 53380-3 : 1998-07 8 Components of diffusion cells 8.1 Joints All joints in me

28、tallic pipes carrying the gas shall be sealed so as to be gastight. Compression couplings have proved very suitable for this purpose. 8.2 Humidification components One of the methods described below shall be used to establish specific humidities in the test gas. 8.2.1 The gas to be humidified shall

29、be passed through saturated salt solutions such as those described in DIN 50008-1, by which a standard atmosphere with relative humidities of 12, 33, 53, 75, 85 and 93 YO, for example, at 23 “C is produced. Gas washing bottles of about 250 cm3 capacity and about one-third full of salt solution (incl

30、uding the undissolved salt) shall be used, the surface area of the salt solution being not less than 15 cm2. The gas inlet shall be positioned below the surface of the solution but above the undissolved salt, allowing the gas flow to be checked by observing the gas bubbles. 8.2.2 The gas to be humid

31、ified shall be passed through distilled water at a suitable temperature. At a test temperature of 23 “C, this produces a relative humidity ranging from 22 YO to 1 O0 YO. A thermostat shall be used to keep the washing bottle at the saturation temperature for the required relative humidity, which can

32、be taken from a water vapour pressure table. 8.2.3 If tests are carried out for a prolonged period at a low relative humidity (less than 50 YO at 23 OC), the sensor (cf. subclause 8.6) may dry out. To prevent this occurring, a small gas washing bottle containing distilled water may be inserted in th

33、e carrier gas stream at the inlet to the sensor (see figure 2 (B). Since the volume of this bottle and the take-up of oxygen in water cause a delay in the steady-state reading both the bottle volume and the quantity of water used shall be minimized. To prevent the specimen from being pressurized, th

34、e end of the carrier gas line shall lie above the surface of the water. 8.3 Components for removal of oxygen from carrier gas Before the carrier gas enters the diffusion cell, it shall be passed through a metal tube (K) containing about 5 g of a 0,5% platinum or palladium catalyst on alumina which c

35、auses any residual oxygen to react with the hydrogen in the carrier gas to form water. If the carrier gas is pure nitrogen (99,99 %) (see subclause 6.1), the metal cartridge shall be filled with an oxygen absorbent. 8.4 Flowmeter A controllable flowmeter (D) having a range from 5 mi/min to 1 O0 mumi

36、n shall be used, enabling the carrier gas flow to be set and monitored. 8.5 Valves Two four-way ball valves (Vl, V2) shall be used for switching the carrier gas and oxygen flow to either the diffusion cell or the sensor. 8.6 Sensor The oxygen which permeates the specimen shall be detected using an o

37、xygen-sensitive coulometric sensor (S) with nickel, cadmium, and graphite electrodes saturated with potassium hydroxide solution. To prevent the potassium hydroxide solution from drying up, humid carrier gas shall be employed, since the response time of the sensor will be otherwise reversibly prolon

38、ged. However, measurements can be carried out for a few days with dry carrier gas without damaging the detector. The oxygen molecules entering the detector react at the surface of the graphite cathode, where each oxygen molecule captures four electrons in the following reaction: O, +2 H,O +4 e-4 OH-

39、 The OH ions then release four electrons as a result of reacting with the porous cadmium anode, as follows: 2Cd+4OH-2Cd(OH),+4e- If the detector is exhausted, it can be regenerated by applying a countervoltage. The detector will be irreversibly damaged by carbon dioxide, which converts the potassium

40、 hydroxide solution into potassium carbonate. NOTE: Other sensors can be used if they fulfil the following requirements: 1. the reading gives approximately 1 O0 YO of the oxygen injected; 2. there is a linear relationship between the output signal and the amount of oxygen injected; Page 6 DIN 53380-

41、3 : 1998-07 3. the range of indication is from 2 . 10-8 g O,/h to 6 . 1 O-4 g O,/h for a flow of 20 cm3/min; 4. the sensor has no resistance up to a flow of about 60 cm3/min; 5. the sensor is insensitive to moisture; 6. no reaction occurs with hydrogen. 8.7 Load resistor The voltage drop shall be me

42、asured across a load resistor through which the current generated by the coulo- metric sensor flows. Typical values for this resistor are 5,03 Q and 50,3 Q, giving a convenient ratio of output voltage to oxygen transmission rate in units of cm3/(m2 . d) or cmVd in the case of hollow bodies. 8.8 Volt

43、age recorder A multiple range strip chart recorder shall be used to measure the voltage drop across the load resistor. The recorder shall be capable of measuring voltages ranging from 0,l mV to 50 mV, at a resolution of 1 pV, and shall have an input impedance of not less than 5 kQ. An equivalent ele

44、ctronic display or evaluation system may also be used. 9 Checking the sensor In principle, four electrons are produced by the coulometric cell for every oxygen molecule. In practice, the detectors generally achieve an approximately 1 O0 YO conversion of the oxygen molecules injected but become less

45、effective if a critical flow of carrier gas is exceeded. The detector may give false readings because of ageing (exposure to carbon dioxide), the electrolyte drying up or because of oxygen breakthrough and shall therefore be checked at regular intervals. A known quantity of oxygen can be fed to the

46、sensor via an inlet valve or using a gastight syringe. The sensor signal (peak) shall be integrated, and the quantity of oxygen recorded shall be compared with that injected. The cause of any errors exceeding 5 YO shall be identified and, if necessary, the sensor shall be replaced. Another very accu

47、rate method of checking the sensor is that of water electrolysis. This involves allowing the carrier gas to flow through an electrolysis vessel in which water is being decomposed electrolytically. The oxygen produced during electrolysis is fed into the sensor and generates a current equal to the cur

48、rent con- sumed in electrolysis. 1 O Calibration constant For a specimen having an oxygen transmission rate of 1 O0 cm3/(m2. d . bar) and a test area of 1 O0 cm2, a standard oxygen volume of 1 cm3 shall be fed to the sensor over a period of 24 hours with an oxygen pressure difference of 1 bar betwee

49、n the sheet surfaces. Since each oxygen molecule generates four electrons, 1 moi of oxygen yields a charge of 4 . 96485 A. s = 3,86 . 1 O5 A . s, according to Faradays law. It follows that 1 cm3 of oxygen (= 1/22393 moi) flowing uniformly through the sensor over 24 h (= 86400s) will generate a constant direct current of I= 3,86 . 1 O5 A. s/moi . (1/22 393 moi) 86400 s = i ,99 . i 0-4 A If this current is passed through a resistor and the resulting voltage drop is 1 mV, the value of the resistor (resistance), R, will be 1 O-3 V/(1,99 . 1 O4 A) = 5,03 Q. The connection between res